1. Field of the Invention
Trisodium carboxymethyloxysuccinate has recently been disclosed as a builder salt to enhance the cleaning power of detergent surfactants, and to replace detergent builder phosphates in cleaning compositions, as set forth in U.S. Pat. No. 3,692,685, assigned to the instant assignee, and incorporated herein by reference.
As explained in the aforesaid patent, the carboxymethyloxysuccinates are biodegradable and non-eutrophying and are excellent substitutes for the established detergent builder polyphosphates which are suspected of being a factor in the eutrophication of lakes, etc. However, the level of fabric detergency to which the consumer has become accustomed from the use of polyphosphate-built detergents is not quite reached in the overall use of trisodium carboxymethyloxy-succinate as a replacement for polyphosphates. Typical of the comparative efficacy are the results shown in a series of experiments designated as Examples 1-10 in the aforesaid U.S. Pat. No. 3,692,685. In this series the detergent effect of the trisodium carboxymethyloxysuccinate-built detergent compositions is shown to vary from 82 to 97% of the detergency of a comparative sodium tripolyphosphate-built detergent composition. The data also indicate that the detergency-enhancing effect of trisodium carboxymethyloxysuccinate is greater on some detergent species than on others.
Sodium citrate has also been suggested as a builder substitute for polyphosphates in detergent compositions. However, sodium citrate possesses the disadvantage that it reacts with sodium hypochlorite at pH levels below about 8.5 where significant amounts of the hypochlorous acid species are present. This disadvantage becomes evident in home laundering since in many instances wherein the soil on the fabric being washed is acidic, the pH of the wash solution drops below 8.5, causing the citrate to become reactive towards any hypochlorite bleach that may be added and thereby, impairing the bleaching efficiency and detergency of the washing operation.
Carboxymethyloxysuccinic acid and its salts, on the other hand, are stable towards hypochlorite in both acidic and alkaline solution and, for this reason, the compositions of the present invention are useful for cleaning fabrics and, particularly in acidic media, for the cleaning and sanitizing of metal surfaces and other hard surfaces such as walls and floors.